1. Field of the Invention
The present invention relates to an ion source device, including an ion engine device and a plasma contact for controlling posture, orbit, and electrification of a man-made satellite, and an ion source generator for an atomic furnace.
2. Description of the Related Art
FIG. 6 is a diagram illustrating an exemplary method for preventing deterioration of an ion source according to related art. The diagram shows an ion source 1 (such as an ion engine device and a plasma contact), ion source purge gas 5 (such as a dry, inactive gas), an ion source sealing vessel 13, an open-type cathode 15, a discharge chamber 16, an opened grid 17, and an ion source device sealing vessel evacuate/gas-exchange device 24. The ion source purge gas 5 contains no, or a harmless level of, virulent gas 7, such as moisture or oxygen in air, which may adversely affect the performance of the ion source 1. The ion source sealing vessel 13 is either filled with the ion source purge gas 5 or else vacuumed to maintain the ion source 1 therein. The cathode 15, the chamber 16, and the opened grid 17 are formed in the inside of the ion source 1. The evacuate/gas-exchange device 24 evacuates the ion source sealing vessel 13 or exchanges the internal gas.
Next, one method used to prevent deterioration of an ion source will be described. In this method, the ion source sealing vessel 13 is initially evacuated using the evacuate/gas-exchange device 24, and is then filled with the ion source purge gas 5. This process is repeatedly carried out. Alternatively, a vacuum is maintained inside the ion source sealing vessel 13 by continuously evacuating the vessel 13 using the evacuate/gas-exchange device 24.
With the above, the virulent gas 7 is prevented from passing through the opened grid 17 and invading further inside to the discharge chamber 16 to deteriorate the inside of the chamber 16 and the open-type cathode 15 in the chamber 16 through contact.
As the opened grid 17, the discharge chamber 16, and the open-type cathode 15 are kept shut away from virulent gas 7 in the ion source 1, as described above, adverse effect due to the virulent gas 7 can be reduced. The adverse effect may include abnormal discharging due to degassing of the gas or moisture having been absorbed while preserving the ion source 1 in air, which may occur at the time of driving the ion source, and life reduction or deteriorated operation characteristics due to the gas or moisture having invaded, while preserving the ion source 1 in air, into the open-type cathode 15, and so on.
FIG. 7 is a diagram illustrating another example of a related method for preventing deterioration of an ion source. The drawing shows an ion source 1, an ion source purge gas supplying device 3, ion source purge gas 5, virulent gas 7 (such as, moisture, oxygen, and so on) which may adversely affect an ion source, a system body 9 (such as a man-made satellite) for incorporating the ion source device, an ion source non-sealing cover 14, an open-type cathode 15, a discharge chamber 16, an opened grid 17, gas discharged state 18 in which the ion source purge gas supplied from the supplying device 3 is discharged into air, a slit 19 formed at the edge of the ion source purge non-sealing cover 14, and a purge gas supplying line 20 through which the purge gas 5 is supplied from the supplying device 3 to the cover 14. The ion source purge gas 5 contains no, or a harmless level of, virulent gas 7. The ion source non-sealing cover 14 is attached to the ion source 1 which remains incorporated into the system body 9. The cathode 15, the chamber 16, and the opened grid 17 are formed in the inside of the ion source 1.
This method for preventing deterioration of the ion source will be described. In this method, the ion source 1 remains incorporated into the system body 9. The ion source purge gas 5 is continuously or discontinuously supplied from the ion source purge gas supplying device 3 via the purge gas supplying line 20 to the ion source purge non-sealing cover 14. The supplied gas 5 passes through the opened grid 17 inside the ion source 1 covered by the non-sealing cover 14, to invade the inside of the ion source 1, in particular, the open-type cathode 15, the discharge chamber 16, and the opened grid 17, and is finally discharged (18) through the slit 19.
With the above, the internal parts of the ion source 1 susceptible to deterioration due to the virulent gas, namely, the open-type cathode 15, the discharge chamber 16, and the opened grid 17, are exposed to the flowing ion source purge gas 5 so that contact of these parts with the virulent gas 7 can be reduced. With an arrangement in which the purge gas 5 is discharged (18) through the slit at the edge 19 of the cover 14, the pressure of the air under the cover 14 can be maintained at a slightly higher level than that outside of the cover 14 by gas flow created around the slit. Backflow of the virulent gas 7 via the slit at the edge 19 into the area under the cover 14 can therefore be prevented.
According to the above method, as the ion source 1 is preserved and remains installed to the body system 9, such that the incorporated open-type cathode 15, discharge chamber 16, and opened grid 17 are kept shut away from the virulent gas 7, adverse effects due to the virulent gas 7 can be reduced. The adverse effect may include abnormal discharging due to degassing of the gas or moisture having been absorbed while preserving the ion source 1 in air, which may occur at the time of driving the ion source, and life reduction or deteriorated operation characteristics due to the gas or moisture having invaded, while preserving the ion source 1 in air, into the open-type cathode 15, and so on.
An ion source 1 as shown in FIG. 6 must be preserved in an ion source sealing vessel 13. That is, the ion source 1 must be preserved under conditions different from those it will operate under, which are the conditions when the ion source 1 is actually installed in a man-made satellite for operation in orbit. Therefore, a process is required to activate the ion source 1 in a preserved state to be in an operation state. Because such a process is required, during which the ion source 1 in its entirity is thus exposed to air which may contain virulent gas 7, adverse effects to the ion source are possible. This may cause a problem such that the inside of the ion source 1, particularly, the discharge chamber 16 and the open-type cathode 15 in the chamber 16 may be brought into contact with air invading through the opened grid 17.
The ion source as shown in FIG. 7 includes an improvement enabling purging of the ion source 9 which remains installed to the system body 9, similar to as is described referring to FIG. 6, so that the discharge chamber 16 and the open-type cathode 15 can be prevented from exposure to air with virulent gas 7 through the opened grid 17 when the ion source 1 removed from the conditions of its preserved state to be set in an installation state in the system body 9.
However, in this purge vessel, where the purge gas flows to covering the entire ion source, the purge gas stagnates near the internal parts of the ion source 1, which are susceptible to the influence of the virulent gas 7, e.g., near the discharge chamber 16 and the open-type cathode 15. In other words, since the purge gas 5 does not pass through the susceptible parts, e.g., the cathode 15, the chamber 16, and the opened grid 17 to purge them, the influence due to the virulent gas 7 to these parts can not be prevented with any reliability.
Further, during the period from the removal of the ion source 1 from the sealing vessel 13, which includes exposure to air with virulent gas 7, to it's installation in the system body 9, thereafter providing the ion source purge gas supplying device 3, the purge gas supplying line 20, and the ion source purge non-sealing cover 14, and until the air is completely exchanged with the ion source purge gas 5 supplied from the supplying device 3, those parts susceptible to adverse influence of the virulent gas 7, e.g., the open-type cathode 15, the discharge chamber 16, and the opened grid 17, remain in contact with the virulent gas 7.
Still further, as any attachments, such as a purge vessel, attached to the ion source 1 must be removed before driving of the ion source device can be started, virulent gas may contact or invade into the ion source 1 after the attachments were removed. In addition, as the purge vessel is of non-sealing type, virulent gas may invade through the slit to contact the ion source while the purge gas supplying device suspends operation.